1. Field of the Invention
This invention relates generally to golf clubs of the type having iron heads for use on tees and in fairways. More particularly, but not by way of limitation, this invention relates to a new and improved structure of the head of the iron club.
2. Description of the Prior Art
A full set of golf irons typically include a set of eleven irons, numbered one (long) through nine (short), a pitching wedge and a sand wedge. Each iron comprises a head including a hosel and a shaft which is attached to the head by fitting the shaft into the bore of the hosel. A grip is fitted to the opposite end of the shaft from the head. The hosel is attached to and is integral with the head. The head includes a heel, a bottom sole, a toe, a planar striking face and a backside.
The eleven irons of a full set conventionally have varying degrees of loft angle and lie angle. The loft angle of an iron is the angle between a vertical plane, which includes the shaft, and the plane of the striking face of the iron. The lie angle of an iron is the angle between the shaft and the ground (horizontal plane) when the tangent to the sole directly under the center of mass is in the horizontal plane and when the shaft lies in a vertical plane.
The loft angle, as the name suggests, determines how much loft is imparted to the ball when it is struck by the tilted striking face. The lie angle of the iron assures that when swung properly, the sole of the iron will contact the ground evenly so that the striking face will not tend to twist inwardly or outwardly.
In a conventional set of irons, each iron has a number of horizontal grooves extending across the planar striking face. The horizontal grooves assist in providing back spin to the golf ball when struck by the planar striking face. When the planar striking face fails to impart back spin to the ball, the ball may flutter and not fly as far as anticipated and will not hold (bite) the playing surface upon landing.
For any set of golf irons, it is important that for a consistent swing, the iron impart consistent loft and distance to the ball. It is also important that when properly swung, the iron produces a consistent shot without a tendency to hook or slice.
Present day iron club designs fall into two general categories; first, the traditional type of design wherein the iron is referred to as the "muscle-back" design and has a generally continuous back portion on the club head; the second type of iron design is referred to as the "cavity-back" design wherein the back portion of the club head includes a substantial depression or cavity which has the effect of providing perimeter weighting for the club head. In contrast with the more conventional solid back iron, perimeter weighting normally provides a larger "sweet spot" or hitting area. That is to say, the cavity-back type of club head is rather forgiving and is designed so that the ball does not have to be struck precisely in the center of mass of the club head to attain acceptable results.
Thus, with present day designs, as we progress through a set of iron clubs starting with the lower lofted irons, the location of the center of mass moves outwardly along the club head away from the hosel and toward the toe of the club head. This variance in the location of the "sweet spot" is an undesirable feature that can adversely affect play. This phenomenon or disadvantage is present not only with the traditional muscle-back irons, but also with the cavity-back irons.
With a cavity-back type of iron, the present day designs utilize a relatively uniform cavity size or dimension from club to club. That is to say, the approximate volume of the cavity for a one-iron will be about the same as that for a nine-iron or pitching wedge. Since the weight of the club head increases as we progress through the clubs of the set, with the cavity volume remaining approximately constant, the increased mass of the club is normally accommodated at two locations. The increased weight is normally placed either on the sole of the club head, or proximate the toe of the club, or portion the weight to both locations. Consequently, there is provided a club head either with a relatively thick sole and/or an oversized, weighted toe portion. Both of these are undesirable features, especially in the higher lofted iron clubs. The placement of increased or excess weight in the sole of the club head causes the ball to fly higher than desired. The addition of weight at the toe location, especially in the higher lofted clubs, is also undesirable as this will cause the face of the club head to close during the golf swing. With the center of mass disposed relatively outwardly toward the toe, the closing of the face of the club head can produce errant shots, or at the very least, shots of lesser accuracy than is demanded, especially by the more skilled players of the game of golf.